1. Field of the Invention
This invention relates generally to the field of treating wells to stimulate fluid production. More particularly, the invention relates to the field of abrasive jet cutting of tubular members in oil and gas wells.
2. Description of the Related Art
Abrasive jet perforating uses fluid slurry pumped under high pressure to perforate tubular goods around a wellbore, where the tubular goods include tubing, casing, and cement. Since sand is the most common abrasive used, this technique is also known as sand jet perforating (SJP). Abrasive jet perforating was originally used to extend a cavity into the surrounding reservoir to stimulate fluid production. It was soon discovered, however, that abrasive jet perforating could not only perforate, but cut (completely sever) the tubular goods into two pieces. Sand laden fluids were first used to cut well casing in 1939. Abrasive jet perforating was eventually attempted on a commercial scale in the 1960s. While abrasive jet perforating was a technical success (over 5,000 wells were treated), it was not an economic success. The tool life in abrasive jet perforating was measured in only minutes and fluid pressures high enough to cut casing were difficult to maintain with pumps available at the time. A competing technology, explosive shape charge perforators, emerged at this time and offered less expensive perforating options.
Consequently, very little work was performed with abrasive jet perforating technology until the late 1990's. Then, more abrasive-resistant materials used in the construction of the perforating tools and jet orifices provided longer tool life, measured in hours or days instead of minutes. Also, advancements in pump materials and technology enabled pumps to handle the abrasive fluids under high pressures for longer periods of time. The combination of these advances made the abrasive jet perforating process more cost effective. Additionally, the recent use of coiled tubing to convey the abrasive jet perforating tool down a wellbore has led to reduced run time at greater depth. Further, abrasive jet perforating did not require explosives and thus avoids the accompanying danger involved in the storage, transport, and use of explosives. However, the basic design of abrasive jet perforating tools used today has not changed significantly from those used in the 1960's.
Abrasive jet perforating tools and casing cutters were initially designed and built in the 1960's. There were many variables involved in the design of these tools. Some tool designs varied the number of jet locations on the tool body, from as few as two jets to as many as 12 jets. The tool designs also varied the placement of those jets, such, for example, positioning two opposing jets spaced 180° apart on the same horizontal plane, three jets spaced 120° apart on the same horizontal plane, or three jets offset vertically by 30°. Other tool designs manipulated the jet by orienting it at an angle other than perpendicular to the casing or by allowing the jet to move toward the casing when fluid pressure was applied to the tool.
The need to sever tubular goods is common in the oil and gas industry. Mechanical cutters and explosive cutters, employed for many years, are still widely used and being improved upon. Mechanical cutters typically employ blades that pivot out from the tool body while the cutting tool is turned by means of a downhole motor. The blades cut through the casing to sever the pipe. Explosive cutters generally employ a shaped charge to tear the pipe into two pieces. Newer chemical cutters employ corrosive chemicals to dissolve the pipe to sever it. More recently, high pressure abrasive fluid cutters have been employed in conjunction with specialized downhole motors to rotate an abrasive fluid stream against the tubing to sever it.
All of these conventional cutting tools have problems associated with their use. Mechanical cutters have size and strength limitations. Explosive cutters introduce the difficulties of purchasing, transporting, and using explosives, particularly in the United States, but also in the rest of the world. Chemical cutters have temperature and pressure limitations. Current abrasive jet cutters typically employ specially-designed downhole motors (to rotate the abrasive fluid jets), which are expensive. Additionally, tight access size restrictions, non-circular or irregular surfaces to be cut, and horizontal and vertical operation pose problems for all the current cutter types.
The following patents and publications are representative of conventional abrasive jet perforating and cutting tools, along with apparatuses and methods that may be employed with the tools.
U.S. Pat. No. 3,145,776 by Pittman, “Hydra-Jet Tool”, discloses protective plates for an abrasive jet perforating tool. The plates, made of abrasive resistant material, are designed to fit flatly to the body of the tool around the perforating jets. The plates are employed to protect the body of the tool from ejected abrasive material that rebounds. The protective plates disclosed in Pittman are not designed to protect the abrasive jets themselves.
U.S. Pat. No. 4,781,250, by McCormick et al., “Pressure Activated Cleaning Tool”, discloses a downhole tool for cleaning tubing, casing and flow lines with pressurized cleaning fluid pumped through coiled tubing. The cleaning tool is rotated by a J-slot indexing tool activated by fluid pressure changes. The McCormick et al. patent does not disclose employing the indexing tool with perforating or cutting tools.
U.S. Pat. No. 3,266,571 by St. John et al., “Casing Slotting” discloses an abrasive jet perforating tool designed to cut slots of controlled length. The slot lengths are controlled by abrasive resistant shields attached to the tool to block the flow from rotating abrasive jets. The St. John et al. patent does not disclose severing tubular members.
U.S. Pat. No. 5,499,678 by Surjaatmadja et al., “Coplanar Angular Jetting Head for Well Perforating”, discloses a jetting head for use in an abrasive jet perforating tool. The jet openings in the jetting head are coplanar and positioned at an angle to the longitudinal axis of the tool. The angle is chosen so that the plane of the jet openings is perpendicular to the axis of least principal stress in the formation being fractured. The tool must be custom-made for each job, since the entire jet head is angled into the tool.
U.S. Pat. No. 5,765,756 by Jorden et al., “Abrasive Slurry Jetting Tool and Method”, discloses an abrasive jet perforating tool with telescoping jetting nozzles. The jetting nozzles are operated perpendicularly to the longitudinal axis of the tool body, although the nozzle assemblies can pivot back into the tool body for retrieval back up the wellbore. The Jordan et al. patent discloses using the perforating tool for removing a casing section, cutting a window, series of longitudinal slots, or plurality of perforations in a wellbore casing, and removing or cleaning a wellbore formation to enhance perforation. The Jordan et al. patent does not disclose severing tubular members.
U.S. Pat. No. 6,564,868 B1, by Ferguson et al., “Cutting Tool and Method for Cutting Tubular Member”, discloses an abrasive jet perforating tool for severing tubular members, such as production tubing. The jetting nozzles are preferably perpendicular to the longitudinal axis of the tool body. The Ferguson et al. patent discloses rotating the cutting tool by means of a downhole motor, such as disclosed in U.S. Pat. No. 6,439,866 B1, by Farkas et al., “Downhole Rotary Motor with Sealed Thrust Bearing Assembly”.
U.S. Pat. No. 7,497,259 B2, by Leising et al., “System and Method for Forming Cavities in a Well”, discloses a downhole assembly string for perforating wells. The string comprises an anchoring mechanism, a multi-cycle vertical incrementing tool, a swivel orienting device and a perforation tool, suspended from coiled tubing. The perforation tool is moved vertically by the incrementing tool, which is activated by fluid pressure changes. The Leising et al. patent does not disclose employing the incrementing tool to rotate the perforation tool.
SPE publication by Loving et al., “Abrasive Cutting Technology Deployed Via Coiled Tubing”, SPE 92866, SPE/ICoTA Coiled Tubing Conference and Exhibition, April 2005, discloses an abrasive jet cutting tool for cutting production tubing, drill pipe, drill collars, completion components, and casing strings. The cutting tool is deployed using conventional coiled tubing and is rotated by pumping an abrasive slurry through a downhole sealed bearing, positive displacement motor mounted above an abrasive cutting head. The abrasive slurry is pumped down the coiled tubing by a conventional high pressure pump.
SPE publication by Hebert et al., “Cutting Concentric Casing Strings with Sand Slurry”, SPE 113734, SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition, April 2008, discloses a case history of cutting a 7-in. liner inside a 9⅝-in. casing with an abrasive jet cutting tool. The jet cutting tool was deployed using drill pipe and a downhole slow-rotating hydroblast motor.
Thus, a need exists for an abrasive jet perforating tool and method of use, in particular for severing tubular members, that can pass through tight restrictions and can be used in small inner diameter pipe. Preferably, the perforating tool does not require an expensive downhole motor or means for rotating the deployment tubing from the surface.